WO2021259877A1

WO2021259877A1 - Device and method for detecting the flocculation threshold of a colloidal medium, in particular a medium comprising asphaltenes, by the addition of aliphatic solvent

Info

Publication number: WO2021259877A1
Application number: PCT/EP2021/066880
Authority: WO
Inventors: Ahmad AL FARRA; Frédéric JOSE; Sandra FANTOU; Jérôme OLIVIER
Original assignee: Total Raffinage Chimie
Priority date: 2020-06-23
Filing date: 2021-06-21
Publication date: 2021-12-30
Also published as: CN115735112A; CA3183002A1; EP4168781A1; US20230251176A1

Abstract

The invention relates to a device (1) for measuring the flocculation threshold of a colloidal medium by means of the addition of an aliphatic solvent, the device comprising: a measuring cell (10) operating by means of direct optical transmission, said measuring cell including a measuring chamber which is defined by fixed walls and intended to receive the medium inside the measuring chamber, a light transmitter (12) configured to transmit a light beam entering the measuring chamber in a transmission direction, a light receiver (14) configured to directly receive the light beam leaving the measuring chamber, optionally an optical element located between the transmitter and the measuring chamber, and a motorised movement member (16) for moving one element chosen from among the transmitter, the measuring cell and the optical element, in a direction parallel to the transmission direction; and a system (20) for managing the motorised movement member, which system is designed to adjust the volume of the measuring chamber through which the light beam passes.

Description

DEVICE AND METHOD FOR DETECTION OF THE FLOCCULATION THRESHOLD OF A COLLOIDAL MEDIUM, ESPECIALLY OF A MEDIUM INCLUDING ASPHALTENES,

BY ADDITION OF ALIPHATIC SOLVENT

5 TECHNICAL FIELD

The subject of the invention is a new method for detecting the flocculation of asphaltenes, as well as an associated detection device for measuring the light in heavy hydrocarbon products, waste oils, dirty water or any product containing an emulsion. and, in particular, for measuring the flocculation threshold of a colloidal medium.

10

STATE OF THE ART

Petroleum products, and in particular fuel oils or petroleum distillation residues, generally called "black products" in the profession, are colloidal systems made up of asphaltenes - that is to say heavy, very aromatic molecules possessing

15 paraffinic side chains - which are dispersed (or also called "peptized") in the form of micelles in an oily phase. These colloidal systems can be destabilized more or less easily, for example by thermal cracking or by dilution. Thus, in a refinery, the conversion process, called visbreaking, can lead to precipitation of asphaltenes under the effect of the high temperatures of the process (generally above

20,400 ° C). Likewise, the constitution of mixtures containing such colloidal systems can generate precipitation of these asphaltenes by flocculation, in particular if the dilution environment is of the paraffinic type.

It is therefore necessary to know or estimate the characteristics of these asphaltenes in black products, such as a petroleum product or a mixture of hydrocarbon products, in order to

25 to assess its intrinsic stability, as well as its associated stability reserve. In fact, the higher the stability reserve, the less the black product will be subject to problems of precipitation of asphaltenes, or of compatibility by dilution with other chemical species, in particular paraffinic bases.

It should be noted that the fuel oils or petroleum residues consist of a maltenic matrix

30 (resins + paraffins) and asphaltenes dispersed in colloidal form. Asphaltenes which have a very aromatic character are insoluble with paraffins which have an aliphatic character. For a residue to be stable, it is necessary for the asphaltenes to be kept in suspension (or dispersed or peptized) in the oily matrix. The peptization of asphaltenes is ensured by resins which have both an aromatic character and a

35 aliphatic character. When a residue has been destabilized, the asphaltenes flocculate by agglomerating in the form of large particles which can generate clogging of filters present in the various treatment units, or even deterioration of the metallurgy, for example the pipes by fouling which leads to to a loss of energy efficiency and the capacity of the pipes.

40 The characteristic called value S (“S-value”), or even intrinsic stability, for example of a black product, is defined in the profession as well as in standard ASTM D7157-18 (Revision 2018) by the following expression :

S = aromaticity of maltenes / aromaticity of asphaltenes, or S = So / (l-Sa), in which, - So represents the power of the medium to dissolve asphaltenes, ie the aromatic character of the medium. The more aromatic it is, the higher the So will be.

- Its is the aromatic character of asphaltenes.

- 1-Sa represents the aromaticity of the medium necessary to dissolve the asphaltenes present.

If S> 1, the asphaltenes are peptized and are therefore stable. S-1 represents the stability reserve (the higher this reserve, the less the black product will be subject to problems of precipitation or compatibility).

The severity of a thermal shock, such as that provided by distillation or visbreaking acts directly on the aromaticity of asphaltenes since thermal cracking causes the cutting of the alkyl chains and the condensation of the asphaltenes. The more condensed and less branched asphaltenes (weaker Sa) will need a more powerful solvent to remain dispersed. Thus, the knowledge of the value of S, linked to that of Sa, will make it possible to specify the settings of the operating conditions of the unit concerned so that it is operated without risk of precipitation of asphaltenes, and consequently, for meet the different quality requirements of the operator.

Furthermore, knowledge of the values of the solvent power So and of the aromatic character of the asphaltenes Sa is necessary in order to optimize the mixing of the various constituents of the fuel oils. Thus, if we add a flux (product capable of lowering the viscosity of a mixture) of low solvent power to a black product, for example visbreaking, and having high So and low values, we reduce the value of the So of the mixture, which can lead to a destabilization of the black product, and consequently to a flocculation of the asphaltenes, because the resulting values So and Sa would be too low to satisfy the relation S> 1, that is to say the condition so that said asphaltenes are peptized, therefore stable.

Usually, the values of S and Sa are determined in the laboratory, then by calculation So, of a black product by a staged dilution using a paraffinic solvent of said black product, mixed beforehand with an aromatic solvent. The moment when flocculation occurs is noted. The measurement is repeated for at least one other mixture with a different dilution rate. We thus obtain results which make it possible by linear correlation to obtain the desired values of S and Sa, then to deduce by calculation So.

Experimentally, the flocculation threshold in a given mixture can be detected by means of several optical probes operating in the infrared (IR) or the near infrared (NIR).

For example, the technique described in patents FR-A-2,596,522 or US-A-4,628,204, from the company Texaco Belgium SA, makes it possible to measure by IR the flocculation threshold of a colloidal solution during its dilution. This measurement first requires the correct choice of the optical measurement probe (there are several probes) depending on the nature and in particular on the presence of more or less asphaltenes in the black product to be tested. In the event of the wrong choice of operator, it is then necessary to proceed to cleaning the apparatus, then to a new preparation of the sample for a new measurement with another probe, which induces a loss of time which can be more than one hour of operator time, while the time for an analysis is approximately 1:30 to 2:00, especially if it is the choice of a different probe that proves to be judicious.

Another example is the method developed by the company Shell, in collaboration with its Dutch partner Zematra, manufacturer of analysis devices. This method, in in which the detection of the flocculation threshold of the colloidal medium is carried out using a single probe, consisting of a single optical fiber surrounded by glass, is unfortunately not usable for the entire range of black products. In fact, the systematic heating of the sample to 150 ° C., in addition to the safety problems, can cause, for certain types of black products, degradations detrimental to the measurement of the flocculation threshold. The time for an analysis is relatively long since it can be greater than 5 hours.

Another method is also proposed for measuring the value of S on black products with a "Porla" device, manufactured by the Finnish company FMS (Finnish Measurement Systems Ltd), and marketed by the English company Med-Lab. This device uses a measuring cell with continuous circulation of the sample to be analyzed with optical detection of the flocculation threshold by means of a prism operating in total reflection. The measurement range is very wide and a result is always accessible, even with black products for which the flocculation threshold is known to be difficult to measure. However, these results are obtained after modifications of the operating parameters of the method, which then become a function of the nature of the product, which is unacceptable when the range of products to be analyzed is very variable, as in the petroleum industry.

Document DE3714755A1 describes a device for measuring the size of flakes in a fluid. The device has a measuring channel located between optical elements which can be moved relative to each other in order to adjust the space between them. The space separating the optical elements further forms an angle in order to retain flakes of different dimensions along the optical elements. The dimensions of this space are thus chosen as a function of the dimensions of the flakes to be measured. A measurement of the luminosity along the optical elements makes it possible to determine the dimensions of the flakes retained between the two optical elements. No measurement of the flocculation threshold is described.

Document US2010 / 053622A1 describes an analysis system making it possible to quantify inhomogeneities contained in a fluid sample. This system uses an optical lens, such as a microscope, to focus a ray of light on the sample. For this purpose, the sample holder can be moved closer or further away from the lens in order to position the sample in a focal plane. The intensity of the light transmitted through the sample is measured by a detector located on the side opposite the lens from the sample. The sample is moved in a predetermined pattern in the focal plane so that the light intensity passing through it is measured along a path representative of the sample. The light intensity is strongly attenuated when it encounters a particle, which allows the characterization and quantification of the particles present in the sample. The displacement of the sample thus has the sole function of detecting the particles.

Document WO2005003754A2 describes an automatic metering apparatus for determining the incompatibility of petroleum products. The detection system consists of a fiber optic light transmission spectrometer, the liquid to be measured passing through an optical cell 100 pm thick which is not detailed. The device is equipped with a circuit connected to several reservoirs and pumps allowing the introduction of a petroleum product, an aliphatic solvent, an aromatic solvent and an auxiliary solvent into a thermostatically controlled mixing vessel used for the dosage. The measurement time of a sample is 1 to 2 hours. There is today a standard (ASTM D7157-18 -Revision 2018) for the determination of the values S, Sa, So, which can be implemented by means of a device and a method described in the document EP1751518 B1 .

Document EP1751518 B1 describes a method for measuring the flocculation threshold in which at least two probes with a light emitter and receiver are introduced into the medium to be measured, these probes operating by optical transmission at the level of detection zones of distinct dimensions. It is then determined which of the two probes is suitable for the measurement by determining the transmission threshold of the medium before addition of aliphatic solvent. Finally, using the probe thus designated, the flocculation is determined after addition of the quantity of aliphatic solvent required for the flocculation. In particular, one of the probes operates in indirect transmission by reflection. The method and the device described make it possible to choose from among several probes introduced into the same medium the probe most suitable for the measurement, in particular after addition of aliphatic solvent. Thus, the device can switch from one probe to another after addition of solvent. These probe changes, which correspond to changes in the optical path traveled by the light beam between an emitter and its receiver, are simple and rapid but can cause oscillations of the signal likely to induce errors in determining the threshold. flocculation. The ROFA ^® company markets a probe having an optical path of adjustable length (probe SVA-130 ^®), which could prevent such oscillations. However, modifying the length of the optical path requires the intervention of an operator, which considerably lengthens the measurement time.

The methods proposed today for measuring the flocculation threshold of asphaltenes in hydrocarbon products therefore have a certain number of drawbacks. They do not necessarily offer the required simplicity, speed and precision of the results, in particular for continuous control of a processing unit, for example visbreaking and / or an efficient mixing unit. They do not allow, either, the direct analysis of a wide range of products according to their asphaltene content. They use techniques which are not easily automated and / or which are not very easy to use.

The present invention aims to remedy one or more of the drawbacks mentioned above.

SUMMARY OF THE INVENTION

The subject of the invention is a device for measuring the flocculation threshold of a colloidal medium by addition of aliphatic solvent, comprising:

- at least one measuring cell operating by direct optical transmission and having a measuring chamber defined by fixed walls, intended to receive the medium inside the measuring chamber, and, associated with each measuring cell: a transmitter of light emitting a light beam entering the measuring chamber in an emission direction, a light receiver directly receiving the light beam leaving the measuring chamber, a motorized displacement member of an element chosen from among the emitter, the measuring cell and an optical element located between the emitter and the measuring cell, in a direction parallel to the emitting direction, a system for managing the motorized displacement member of each measuring cell arranged to adjust the volume of each measuring chamber crossed by the light beam.

The management system thus makes it possible to modify the volume of the measurement chamber crossed by the light beam, in other words the optical path traveled, and this for a single measurement cell associated with a transmitter and a receiver, the volume of the measurement chamber. measure by itself remaining fixed. Thus, only one probe is necessary to measure more or less absorbent products, which makes it possible to avoid the oscillations observed with the device described in document EP1751518 B1. The management system can in particular make it possible to adjust the illuminated volume of a measuring chamber between a minimum value corresponding to a predefined fraction of the volume of the measuring chamber and a maximum value corresponding to the entire volume of the measuring chamber or to a fraction of the volume of the measuring chamber greater than the fraction previously mentioned.

In addition, the measuring cell operates by direct optical transmission, in other words the light beam emitted by the emitter is received directly by the receiver, without an intermediate optical reflection device.

The use of a motorized displacement member and of a management system allows automation of the operation of the device and thus eliminates the need for an operator.

Advantageously, the management system can be arranged to modulate the light intensity of the light beam emitted by the emitter, in other words the quantity of light emitted in the direction of emission. More precisely, by “light intensity” is meant the energy intensity, namely a radiometric quantity which is the measure of the power (or energy flux) of an electromagnetic radiation emitted by a quasi-point source, per unit of solid angle, in a given direction. Its unit in the international system is the watt per steradian (W sr ^_1 ). In particular, the modulation of the light intensity mentioned above is the variation of the energy intensity (the power radiated in the emission cone) obtained by varying the electric current passing through the emitter. When the emitter is a light emitting diode, the energy intensity is almost proportional to the electric current flowing through the diode.

In addition, the measuring chamber of each measuring cell having fixed dimensions, these can be chosen so that the light beam passes through a predetermined quantity of material, for example greater than that of existing probes, thus improving the accuracy of the device even when the volume crossed by the light beam is at a minimum value.

It will be noted that the management system can be linked to other elements of the device and arranged to command / control them, such as the transmitter (to control the light intensity of the light beam emitted), the receiver (to record the signals emitted), temperature sensors, a device for regulating the temperature of the medium, or else to solenoid valves, or even to devices for circulating fluids, to control the distribution of fluids and possibly their circulation, in particular when the device comprises a circuit as described below.

Advantageously, each measuring chamber can have two fixed optical elements forming opposite walls, the associated emitter and detector being located outside the measuring chamber, in particular each facing an optical element in the direction of emission. By optical element is meant an element capable of being crossed by a light beam, in particular without absorbing it.

In certain embodiments, an optical convergence element could be provided between the measuring chamber and the detector in order to make the light beam exiting the measuring chamber converge on the detector. This optical convergence element is therefore located outside the measurement chamber.

In particular, each of the optical elements can be chosen from a plate with parallel faces, a spherical lens and an aspherical lens. Preferably, a blade with parallel faces and an aspherical lens can be chosen.

In particular, when the measuring chamber has two plates with parallel faces, an optical convergence element can be advantageously arranged between the measuring chamber of the measuring cell and the receiver in order to make the light beam exiting the chamber converge on the receiver. . This optical convergence element comprises for example a lens.

According to one embodiment, each motorized displacement member moves the associated transmitter, the latter emitting the light beam directly onto the measuring chamber.

Advantageously, the measuring device can comprise at least one temperature sensor and at least one temperature regulation member connected to the management system and the management system can be arranged to regulate the temperature of the medium.

Advantageously, each measurement cell can comprise a fluid inlet and a fluid outlet connecting the measurement chamber to an associated fluid circuit equipped with a device for circulating the fluid. In other words, each measuring chamber of a measuring cell then forms part of a fluid circuit specific to the measuring device according to the invention, which is not in communication with other circuit (s). of fluid.

Such a fluid circuit can be formed from one or more conduits connected to one another.

In particular, each fluid circuit can include one or more of the following elements:

- at least one tank and at least one liquid injection line connected to each tank, optionally connected to the circuit by a valve, in particular a solenoid valve,

- a mixing chamber having an inlet and an outlet connected to the fluid circuit,

- at least one temperature regulator.

This temperature regulator can be chosen from a heat exchanger, a heating resistor, a Peltier effect device or the like.

Advantageously, the fluid circuit can form a closed loop inside which the medium circulates.

The measuring device according to the invention makes it possible to carry out measurements in a very short time, making continuous measurements possible. This measurement time can be of the order of a millisecond, for example 0.5 ms.

Also, advantageously, the device can comprise means for continuously injecting liquid, and in particular at a constant flow rate, inside the fluid circuit, in particular inside conduits of the fluid circuit. This allows continuous injection of the aliphatic solvent inside the circuit. Such continuous injection while the liquid is circulating at the interior of the circuit makes it possible to rapidly obtain a homogenization of the mixture. Due to the very short measurement time, it is then possible to carry out a measurement by means of the measurement cell while the liquid is circulating inside the fluid circuit, without ceasing to add the solvent, the latter being injected with a low constant flow. This homogenization will be all the more rapid the more the solvent is injected inside the pipes of the circuit. These injection means can comprise an injection line, a pump and a solenoid valve.

The device according to the invention may have two or three identical measuring cells, each associated with a transmitter, a receiver and a motorized displacement member, each cell being connected to its own fluid circuit. The motorized displacement members of the measuring cells can be controlled by the same management system.

A further subject of the invention is a method for measuring the flocculation threshold of a colloidal medium by addition of aliphatic solvent using the device according to the invention, comprising the step of determining, using the measuring cell of said device, the flocculation threshold after addition of the quantity of aliphatic solvent required for the flocculation.

The invention also provides a method for measuring the flocculation threshold of a colloidal medium by addition of aliphatic solvent, in particular paraffinic, comprising the following steps:

(i) the medium is introduced inside a measuring chamber defined by fixed walls of a measuring cell operating by direct optical transmission, the measuring cell forming part of a device for measuring the flocculation threshold further comprising, associated with the measuring cell: a light emitter emitting a light beam entering the measuring chamber in an emission direction, a light receiver directly receiving the light beam exiting the measuring chamber, a member motorized displacement of an element chosen from among the emitter, the measuring cell and an optical element located between the emitter and the measuring cell, in a direction parallel to the emission direction, the measuring device further comprising a system for managing the motorized displacement member of the measuring cell arranged to adjust the volume of each measuring chamber crossed by the light beam and optionally to adjust a light intensity emitted by the transmitter,

(ii) the volume of the measuring chamber crossed by the light beam, and optionally a light intensity of the emitter, is automatically adjusted using the management system so as to obtain a signal detectable by the receiver,

(iii) the flocculation threshold is determined using the flocculation measuring device after addition of the quantity of aliphatic solvent necessary for the flocculation.

This method can be implemented by the device of the invention.

The device for measuring the flocculation threshold according to the invention makes it possible to carry out measurements in a sufficiently short time to allow measurements to be taken while the aliphatic solvent is being added. Thus, advantageously, during step (iii), the aliphatic solvent can be added continuously and the measurements are carried out using the measuring device while the aliphatic solvent is being added. In particular, the aliphatic solvent can then be injected inside a fluid circuit, in particular inside conduits of the latter, the fluid circuit being connected to the measuring chamber of the measuring cell, this fluid circuit being equipped with a device for circulating the fluid.

Advantageously, these continuous measurements can be carried out at a constant flow rate of aliphatic solvent.

Advantageously, the probes can be probes emitting in the NIR range and the occurrence of flocculation is determined by determining the absorption peak.

Advantageously, the method can be implemented at an adjustable predetermined temperature, for example by means of a temperature regulator. This can make it possible to heat the product, for example to facilitate its dissolution, for example before addition of the aliphatic solvent, but to carry out the measurement at a lower predetermined temperature.

Advantageously, the method can comprise a step of diluting (ii) the colloidal medium with a predetermined quantity of aliphatic solvent prior to step (i).

According to one embodiment, the colloidal medium comprises asphaltenes.

The invention also provides a method for determining the stability of a mixture comprising asphaltenes by carrying out at least twice the method for measuring the flocculation threshold of a colloidal medium according to the invention on a medium containing the mixture. and a given amount of aromatic solvent, at different dilution rates. The method for measuring the flocculation threshold can in particular be implemented at least twice successively in the same measuring cell of a measuring device or be implemented simultaneously in two or more identical measuring cells of the same device. of measurement.

According to one embodiment, the aromatic solvent / aliphatic (in particular paraffinic) solvent couple used is the toluene / n-heptane couple.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a representation of the aromaticity graph of the solvent as a function of the inverse of the dilution, i.e. the precipitation curve of a black product which, at a determined dilution rate of this same black product, combines the minimum aromaticity of the solvent necessary so that the mixture does not precipitate.

FIG. 2 is a schematic representation of a device according to one embodiment of the invention.

FIGS. 3a and 3b are schematic representations of a measuring cell according to one embodiment of the device of the invention, in which the transmitter occupies different positions.

FIG. 4 is a schematic representation of a measuring cell according to another embodiment of the device.

FIGS. 5a, 5b and 5c respectively represent the values S, Sa and So of the black product BP3 as a function of the number of tests. FIGS. 6a, 6b and 6c respectively represent the values S, Sa and So of the black product BP14 as a function of the number of tests. All these figures have the same legend, shown only in FIG. 5a.

DETAILED DISCLOSURE OF EMBODIMENTS OF THE INVENTION

With reference to FIG. 1, the method using the device described in document EP1751518 B1 for determining the values of S, So and Sa, for a given mixture of black product, is described. The intrinsic stability of any colloidal system is quantified by dilution with the aid of a paraffinic solvent of a black product, such as fuel oil, an atmospheric distillation residue of petroleum (or under vacuum), a crude oil, previously mixed with an aromatic solvent. This intrinsic stability (S) depends on the aromatic character of the asphaltenes (Sa) and on the aromatic character of the medium (So), as has been described above. The intrinsic stability S of a colloidal system is thus determined by measuring the flocculation threshold of at least 2 different mixtures. From at least these 2 points, we draw a straight line, called the precipitation of a black product (fig 1), which gives access to the parameters Sa and S, then by calculation, to the value So.

By adding a paraffinic solvent to the black product, the mixture becomes unstable from a certain dilution rate Xmin, called "minimum dilution rate".

The following definitions are used, as defined in ASTM D7157-18 (Revision 2018):

Dilution rate X (ml / g): volume of total solvent (aromatic + paraffinic) in milliliters / mass of black product in grams.

- intrinsic stability S of the black product:

S = l + Minimum dilution rate. Here we find the notion of S-l as a stability reserve.

For the experimental measurements, two types of solvents are used, the first is aromatic, consisting essentially of aromatic molecules for the dilution of the sample (for example toluene, xylene, or even 1-methylnaphthalene) and the second is aliphatic of the solvent type paraffinic (for example n-heptane, cetane, or also iso-octane) to cause flocculation of asphaltenes.

The FR flocculation rate ("flocculation ratio") is defined as follows:

FR = volume of aromatic solvent / volume of total solvent.

The ability of asphaltenes to be peptized (“peptizability of an asphaltene”) is defined by: Sa = 1 - FRmax, where FRmax is the maximum flocculation rate (at 1 / X = 0).

We call the precipitation curve the function of the flocculation rate FR as a function of the dilution rate, i.e. here:

1-Sa = f (l / X) = A + B / X.

A and B are constants which depend only on the sample and provide access to the values of S, So and Sa.

We proceed as follows. The starting point is a first mixture of a given mass of black product in a given quantity of aromatic solvent and a paraffinic solvent is added in successive increments. The flocculation threshold is determined (in particular by a method using an IR probe) and the dilution rate and the FR flocculation rate associated with the mixture analyzed are then noted. We obtain a first point, identified by point PI on the graph (fig 1). The operation is repeated, with a starting product which is initially less strongly diluted in the aromatic solvent. We then obtain another measurement materialized by point P2. With the two points PI and P2 it is then possible to draw the line passing through these points and to obtain limit values (1-Sa) on the ordinate axis (FRmax or infinite dilution rate) and 1 / (S -1) on the x-axis (zero FR). It then becomes possible to access the values of S, Sa then So by calculation. This technique, which refers to the standardized method ASTM D7157-18 (Revision 2018), and which consists of the construction of a precipitation curve, from at least two measurement results (three in the standard), for then determining the values of the limit and zero aromaticities is that generally followed in the invention. The masses, volumes and products used are quite conventional in the art of this type of analysis.

With reference to FIG. 2 and to FIGS. 3a, 3b, 4, the device (1) according to the invention comprises a measuring cell (10) operating by direct optical transmission having a measuring chamber (101) of fixed dimensions, defined by fixed walls.

The device (1) also comprises, associated with the measuring cell (10), a light emitter (12) emitting (configured to emit) a light beam entering the measuring chamber (101) in an emission direction ( D) and a light receiver (14) directly receiving the light beam leaving the measuring chamber (101). In other words, the light receiver (14) is positioned so as to directly receive the outgoing light beam. It can in particular be positioned in the emission direction (D), on one side of the measuring chamber (101) opposite to the side where the light emitter (12) is located, as shown in the figures. The emitter is a conventional IR emitter, for example a light-emitting diode, as is the receiver, the latter being a photoelectric receiver capable of delivering a current when it receives a light flux. The useful diameter of the emitter is in particular 4.0-5.0, for example 4.7-4.8 mm.

The device (1) also comprises a motorized displacement member (16) of an element, here the emitter (12), in a direction parallel to the emitting direction (D) of the emitter. The motorized displacement member, configured to move an element, is for example an electric motor, in particular a stepping motor. The axis (17) of this motor can be connected to the transmitter (12) in order to move it in translation, the transmitter (12) being for example supported on a mobile base (18), for example mounted on rails (not shown).

In the embodiment shown, the device (1) further comprises a management system (20) of at least the motorized displacement member (16) allowing the automation of the adjustment of the volume of the measuring chamber crossed by the motor. light bleam. It is therefore not a question of modifying the volume of the measuring chamber, which is fixed, but only the volume of the portion of the measuring chamber illuminated by the light beam. In the example, the management system is also arranged to control the light intensity emitted by the emitter (12).

This management system (20) can comprise one or more processors of the microprocessor, microcontroller or other type, for example forming part of a computer. The processor or processors include in particular computer program execution means suitable for implementing the method described in the present invention.

In one embodiment, the management system can be arranged to receive data. The management system can also be arranged to transmit data, in particular to a display device such as a screen. The management system can thus include one or more input, output, or input / output interfaces. These can be wireless communication interfaces (Bluetooth, WIFI or other) or connectors (network port, USB port, serial port, Firewire ^® port, SCSI port or other).

In one embodiment, the management system may include storage means which may be a random access memory or a RAM (standing for “Random Access Memory”), an EEPROM (standing for “(Electrically-Erasable”). Programmable Read-Only Memory ”), flash memory, external memory, or the like. These storage means can in particular store the data received, and possibly computer program (s).

In the embodiment shown, unlike the existing usual probes, the measuring chamber (101) is part of the measuring cell (10) but is not defined by the transmitter (12) and the receiver (14). that it is located between these allowing the light beam to pass through the measuring chamber. The measuring chamber (101) is here defined in part by two fixed optical elements (102, 103) which form opposite walls of the measuring chamber. In other words, the emitter and the receiver are located outside the measurement chamber and are separate from it.

A first optical element (102) located on the side of the emitter (12), here a plate with parallel faces, allows the transmission of the light beam coming from the emitter (12) to the sample located inside the measuring chamber (101). A second optical element (103) located on the side of the detector (14), here an aspherical lens, makes it possible to focus the light beam transmitted by the sample on the detector (14).

Other pairs of optical elements listed above can be envisaged, however, the configuration of the example has the advantage of being particularly efficient. These different optical elements can be made of glass, polymer, metalloid, but also of hybrid material (glass / polymer).

In the example, the transmitter (12) is movable in translation and moved by means of the motorized displacement member (16). The measuring cell (10) and the detector (14) are fixed. The emitter (12) can in particular be moved between: a first position (FIG. 3a) in which the emission cone (Cl) of the light beam is maximum so that all, or almost all, of the volume ( VI) of the measuring chamber (101) is crossed by the light beam, and a second position (fig.3b) in which the emission cone (Cl) of the light beam has a smaller apex angle so that only a portion (V2) of the volume of the measuring chamber (101) is crossed by the light beam.

It will thus be understood that the displacement of the emitter makes it possible to adjust the volume of the measuring chamber (101) crossed by the light beam.

In both positions, it will be noted that the transmission cone of the light beam C2 converges on the fixed detector (14).

As a variant, the motorized displacement member (16) could move the measuring cell (10), the emitter and the detector being fixed, or alternatively, as shown in FIG. 4, an optical element (15), for example a lens , located between the fixed transmitter (12) and the fixed measuring cell (10). In this case, the half-angle at the top of the cone of light arriving on the measuring chamber can be varied by bringing the lens closer or further away from the measuring cell (10). It will thus be understood that the optical element (15) is optional.

In the embodiment shown, the device (1) further comprises two temperature regulating members (22), here a heat exchanger inside which a refrigerant liquid (23) can be circulated, for example, and a heater (24). This heater could also be located around the mixing chamber (113) described below, such as a thermostat block or the like. It also comprises one or more temperature sensors (25), for example a temperature sensor located at the level of the heat exchanger and a temperature sensor at the level of the measuring cell, to the inlet or the outlet thereof, or in the fluid circuit as shown. The invention is not however limited by a particular position of the temperature sensors. One could in particular be positioned upstream of the measuring chamber with respect to the circulation of the fluid.

These elements can be controlled by the management system (20) which can then be arranged for automatic management of the temperature of the medium.

The measuring cell (10) could be immersed in the medium so that the latter completely fills the measuring chamber. However, preferably, as shown in Figures 2 to 4, the measuring cell (10) comprises a fluid inlet (104) and a fluid outlet (105) connecting the measuring chamber (101) to a circuit. fluid (106), which is equipped with a fluid circulation member (107), here a peristaltic pump (107) controlled by a stepping motor (108). The measuring chamber can thus be in the form of a simple pipe open at both ends, with a closed cross section.

More particularly, in the example, the fluid circuit (106) comprises: a first liquid injection line (109) connected to a reservoir (110) for the injection of a first solvent, for example the aromatic solvent , a second liquid injection line (111) connected to a second reservoir (112) for the injection of a second solvent, for example paraffinic solvent, a mixing chamber (113) having an inlet (114) and an outlet (115) connected to the fluid circuit (106), to receive the medium, the temperature regulator (22) and the heater (24) mentioned above.

The injection lines (109) and (111) can be equipped with solenoid valves (116), (117), and a pump (118, (119) which are preferably controlled by the management system (20) for automation of the device.

The fluid circuit (106) here forms a loop which can therefore be closed for the circulation of the medium inside the loop, for example in the direction of circulation symbolized by the arrows in FIG. 2.

A system for heating the mixing chamber and a reflux column can optionally be provided to enable the product contained in the chamber to be heated to reflux in order to facilitate dissolution of the sample.

The operation of the device according to the invention is described below.

The sample to be analyzed is introduced inside the measuring chamber of the measuring cell of the device according to the invention. In the device shown, the sample is introduced into the mixing chamber before it is circulated in the circuit and inside the measurement chamber. In particular, the volume of product is sufficient to completely fill at least the measuring chamber.

In the example, this introduction step is followed by a step of adding the aromatic solvent to the product to form the medium to be analyzed. The sample is then diluted with the aromatic solvent before circulating inside the measurement chamber of the measurement cell.

An adjustment step is then carried out during which the volume of the measurement chamber of the measurement cell through which the light beam passes through is adjusted, before the addition of paraffinic solvent, that is to say before the flocculation. . We can advantageously also adjust the light intensity emitted by the transmitter. This adjustment step makes it possible to obtain a signal detectable by the receiver. During this step, it is preferably possible first to adjust the light intensity emitted by the transmitter and then to adjust the volume in order to obtain a detectable signal. By detectable signal is meant a signal which can be distinguished from background noise and which is not saturated.

Finally, the flocculation threshold is determined using the flocculation measuring device after addition of the quantity of paraffinic solvent required for the flocculation. To this end, the paraffinic solvent is gradually added and the drop in transmission corresponding to the flocculation of the asphaltenes is noted. This determination is made by conventional techniques, for example by measuring the absorption peak.

The adjustment of the volume of the measuring chamber crossed by the light beam is carried out automatically, by a computer program predetermined when the device is constructed. This automatic adjustment may include adjustment of the light intensity emitted by the emitter.

It may in fact be preferable to modulate the light intensity emitted by the emitter in order to reach a reference value corresponding to a minimum value measurable by the detector. This adjustment of the light intensity can be obtained by varying the intensity of a direct current supplied to the emitter.

In a known manner, a detector can detect a light beam within a determined detection range, corresponding to a percentage of the light emitted by the emitter: below the minimum value of this range, no signal is detected, above of the maximum value of the range, saturation of the receiver leads to a loss of sensitivity. The setpoint is generally chosen in a part of the detection range close to the minimum value.

The adjustment is for example carried out as follows. The light intensity emitted by the emitter is first of all set to its minimum value, corresponding for example to a current of 6mA, the volume of the measurement chamber crossed by the light beam being at a maximum value, for example of the order of 500pl. The light intensity emitted by the emitter is then increased until the setpoint or a maximum value of the light intensity emitted, corresponding for example to a current of 100mA, is reached. When the setpoint cannot be reached by increasing the light intensity emitted up to this maximum value, the volume of the measuring chamber is gradually reduced until the setpoint is reached or up to a value. minimum volume, for example of the order of 10mI. The measurements will then be carried out under these conditions. In particular, the light intensity emitted by the emitter and the volume of the measurement chamber remain fixed as the dilution with the paraffinic solvent proceeds. In this way, the signal can be measured with good precision with a single, suitably set measuring cell, which offers a significant time saving for the operator.

The minimum value of the light intensity emitted by the emitter corresponds for example to a value below which the precision of the measurement is too low to make it possible to distinguish a signal from the background noise. This minimum value corresponds for example to a current of 6mA.

The minimum value of the volume of the measurement chamber corresponds for example to 10mI. It can be determined experimentally by measurements with very opaque. This minimum volume could be increased in order to allow / improve the detection of flocculation of media containing very small amounts of asphaltenes.

According to an advantageous embodiment, notably implementing the device described with reference to the figures, the introduction step comprises a dissolution phase, during which the medium is introduced inside the mixing chamber ( 113), in an amount sufficient to completely fill the circuit (106), then the temperature of the medium is regulated to a dissolution temperature by means of the temperature regulating member (22) and the heating member (24 ), or by means of a temperature regulator surrounding the mixing chamber (113). The medium contained in the mixing chamber (113) can also be kept under agitation. The aromatic solvent is then injected inside the circuit and the medium and the aromatic solvent are circulated in the circuit (106) by means of the pump (107) for sufficient time to obtain a homogeneous mixture.

This dissolution phase can optionally be followed by a pre-dilution phase with the paraffinic solvent, during which a predetermined quantity of this solvent can be injected into the circuit. This is done in the case of a very aromatic and stable product or when the product is too dark and the light intensity emitted by the detector reaches its maximum without having detected the flocculation volume.

A cooling phase is then carried out during which the temperature is regulated to a predetermined test temperature by means of the temperature regulating member (22).

A metering phase is then carried out during which the paraffinic solvent is gradually added. This addition of solvent can be accomplished by incremental additions or by continuous addition. The detector signal is then acquired and recorded either after each addition of solvent, or during addition of the solvent. In the latter case, the rate of introduction of the solvent inside the circuit may be constant, for example of the order of 1 ml / minute. It will be noted that the product to be analyzed circulates in the circuit during the addition of the solvent and the acquisition of the signal. This dosing phase can be stopped by an operator, when the maximum volume of the mixing cell is reached or when a predetermined number of incremental additions has been made or when a predetermined volume of solvent has been added.

A cleaning phase can then be carried out, for example by circulating the aromatic solvent in the circuit.

The invention is described with reference to a device comprising a single measuring cell. It will however be noted that the device of the invention can comprise several identical independent measuring cells, for example three, in order to simultaneously carry out three tests on a product in parallel.

In addition, the device according to the invention makes it possible to obtain a possible spectral field of application for the measurements which is very wide. The device according to the invention is suitable for determining the values of S, Sa and So for all types of residues and fuels and is practically not limited as to the nature of the medium to be tested. As the device comprises a single type of measuring cell, it is possible to carry out several measurements to measure the same product in a shorter time. We can thus carry out measurements and thus obtain 3 points of the curve and thus a good repeatability of the measurements for S, Sa and So. Finally, the determination method according to the invention can be carried out at room temperature or at a predetermined temperature, which makes it possible to measure the parameters S, Sa and So at a given temperature and to check their evolution as a function of the temperature, since the stability of asphaltenes depends on the temperature.

In general, the aromatic solvent / paraffinic solvent pair used in the invention is the toluene / n-heptane pair.

EXAMPLES

The following examples illustrate the invention without limiting it.

Example 1

Measurements were carried out on 13 samples of different black products for which the S, Sa values were measured and So calculated, on the one hand with a method using the SVA-130 ^® probes proposed by the company ROFA using the method described in ASTM D7157-18 (Revision 2018) ("Measurement method A" in Table 1 below) and on the other hand with the device and method according to the present invention ("Measurement method B" ).

The device according to the present invention is of the type described with reference to Figures 2 and 3. The measuring cell comprises in particular a plate with parallel faces and an aspherical lens, the distance between the window and the lens being 0.5 mm at the center and 3 mm at the edges.

The volume of the circuit loop here is 4ml. The measurements are carried out while the fluid is circulating at a speed of approximately 10 m L / min. The test temperature here is ambient temperature. It is possible to heat the aromatic solvent / product mixture to accelerate the dissolution of the latter, in particular in the case of vacuum residues. Heating from 60 ° C to 100 ° C is sufficient to dissolve the product in this case in a few minutes. In certain cases (very stable products), a pre-dilution with n-heptane was carried out before the start of the measurements in order to avoid saturation of the detector.

In this example, the black products marked BPI at BP13 correspond to:

BPI: Visco-reduced atmospheric residue low pre-fluxed sulfur content (pre-diluted with a flux);

BP2: Atmospheric residue Visco-reduced high pre-fluxed sulfur content;

BP3: Atmospheric residue Visco-reduced high pre-fluxed sulfur content;

BP4: Visco-reduced vacuum residue;

BP5, BP7, BP8: residue in vacuo;

BP6: Low sulfur vacuum residue;

- BP9, BP11: slurry;

BP10, BP12, BP13: very unstable fuel oil mixtures.

It is noted that the values obtained with the measurement method B according to the invention are close to the values obtained with the measurement method A, the SVA-130 ^® probes allowing implementation of the standard ASTM D7157-18 (Revision 2018) in compliance with the repeatability and reproducibility conditions defined in this standard.

For each of the 13 measurements, the correlation coefficient R ² of the precipitation curve (rate of flocculation FR as a function of the inverse of the dilution) constructed with 3 points (PI, P2 and P3) varies from 0.9817 to 0 , 9999, which is higher than the ^{minimum R 2} value (0.98) required by the standard. In addition, the automation of the analysis makes it possible to carry out the complete analysis in less than an hour with the measurement method B according to the invention while it takes more than two hours for the method A in particular due to the operator time required to modify the optical path of the SVA-130 ^® probes. In addition, the measurement method B according to the invention is also faster than using a device and a method in accordance with document EP1751518 B1 due in particular to the automation of the dilution.

Table 1 Comparison of the results of the S and Sa measurements, and of the calculation of So, with the ROFA SVA-130 ^® probes (Measurement method A) and the device and method in accordance with the invention (Measurement method B)

Example 2

In order to compare the values of the repeatability obtained on the measurements of S, Sa then of the calculated So, accessible by the method using the ROFA SVA-130 ^® probes (Measurement method A) and the automated one which the device and the method make the object of the present invention (Measurement method B), 2 samples BP3 and BP14 were chosen, sample BP3 is defined in example 1, sample BP14 is a crude from Kuwait, liquid at a temperature below 30 ° C.

Tables 2 and 3 below bring together the mean values calculated for 11 separate measurements for the measurement method B according to the invention and the average values calculated on ten or so separate measurements for the measurement method A. The repeatability values and of reproducibility calculated using the formulas in ASTM D7157-18 (2018 Revision) from the mean calculated for the measurements of each of the measurement methods A and B are also shown in these tables. Tables 2 and 3 also show the standard deviation for the 11 measurements of measurement method B, as well as the repeatability calculated according to the general formula: 2 x square root of 2 x standard deviation, i.e. 2.83 x standard deviation. The efficiency shown in these tables is the ratio of the ASTM repeatability (according to ASTM D7157-18 - 2018 Revision) to the repeatability calculated with the general formula.

FIGS. 5a, 5b and 5c respectively represent the values S, Sa and So of the black product BP3, FIGS. 6a, 6b and 6c respectively represent the values S, Sa and So of the black product BP14 for the 11 measurements.

On each of these figures are represented: high and low limits of S, Sa and So taking into account repeatability (high and low repeatability limits), calculated respectively by adding and subtracting the repeatability value calculated for the method of measurement B to the average of the measurements calculated for measurement method B, of the high and low limits S, Sa and So taking into account reproducibility (high and low limits of reproducibility), calculated respectively by adding and subtracting the reproducibility value calculated for the measurement method B to the average of the measurements calculated for the measurement method B, the average of the values obtained with the measurement method B according to the invention (Average B), the values obtained with the measurement method B according to the invention (Values B), the average of the values obtained with the measurement method A (Average A).

It is thus noted that the values appearing in tables 2 and 3 are relatively close between the measurement methods A and B, as also shown by curves 5a, 5b, 5c relating to the sample BP3 and curves 6a, 6b, 6c relating to sample BP14.

Furthermore, the notion of efficiency expressed in Tables 2 and 3 makes it possible to compare whether the repeatability of standard ASTM D7157-18 (Revision 2018) is smaller or greater than the repeatability specific to the device according to the invention. In particular, the smaller the repeatability, the more repeatable the values and therefore less variable. It will be noted in particular that the value of the efficiency is always greater than 1, which means that the repeatability of the device according to the invention is smaller than the repeatability of standard ASTM D7157-18 (Revision 2018).

In each FIG. 5a, 5b, 5c, 6a, 6b, 6c, it can be seen that the minima and maxima of the curves of the tests carried out according to the measurement method B are situated between the low and high limits of repeatability and reproducibility. In other words, the differences in values between several measurements obtained with the measurement method B according to the invention are small for the two types of products.

Table 2 Repeatability measurements on the S, Sa and So values on the BP3 sample obtained with the ROFA SVA-130 ^® probes (Measurement method A) and the device and method in accordance with the invention (Measurement method B)

Table 3 Repeatability measurements on the S, Sa and So values on the BP14 sample obtained with the ROFA SVA-130 ^® probes (Measurement method A) and the device and method in accordance with the invention (Measurement method B)

Example 3

The device according to the invention has also been tested with products containing less than 0.5% by mass of asphaltenes:

BP15: Brut arabe extra light containing 0.45% by mass of asphaltenes BP16: crude Olmelca containing 0.3% by mass of asphaltenes.

Table 4 collates the values S, Sa and So obtained. For each of the measurements, the correlation coefficient R ² of the precipitation curve is greater than 0.98. This example demonstrates that the device according to the invention makes it possible to determine the flocculation threshold of black products, even at very low asphaltene contents.

Table 4 Determination by measurement method B of the S, Sa and So values for the raw materials PB15 and BP16.

Claims

1. Device for measuring (1) the flocculation threshold of a colloidal medium by addition of aliphatic solvent, comprising: at least one measuring cell (10) operating by direct optical transmission and having a measuring chamber (101) defined by fixed walls, intended to receive the medium inside the measuring chamber, and, associated with each measuring cell: a light emitter (12) configured to emit a light beam entering the measuring chamber following a direction of emission, o a light receiver (14) directly receiving the light beam leaving the measuring chamber, o optionally an optical element located between the emitter and the measuring cell, o a motorized displacement member (16) of an element chosen from among the emitter, the measuring cell and the optical element, in a direction parallel to the emission direction, a management system (20) of the motorized displacement member of each measuring cell arranged to adjust the volume of each measurement chamber crossed by the light beam.

2. Measuring device (1) according to claim 1, characterized in that each measuring chamber (101) has two fixed optical elements (102, 103) forming opposite walls, the associated transmitter and detector being located outside. of the measuring chamber, optionally each measuring chamber (101) is defined by two optical elements, each chosen from a plate with parallel faces, a spherical lens and an aspherical lens.

3. Measuring device (1) according to claim 1 or 2, characterized in that the management system is arranged to modulate the light intensity of the light beam emitted by the emitter.

4. Measuring device (1) according to any one of claims 1 to 3, characterized in that each motorized displacement member (16) moves the associated emitter, the latter being configured to emit the light beam directly on the measuring chamber.

5. Measuring device (1) according to any one of claims 1 to 4, characterized in that it comprises at least one temperature sensor (25) and at least one temperature regulating member (23, 24) connected to the management system (20) and in that the management system (20) is arranged to regulate the temperature of the medium.

6. Measuring device (1) according to any one of claims 1 to 5, characterized in that each measuring cell (10) comprises an inlet (104) and an outlet (105) for fluid and in that the device measuring chamber (1) comprises a fluid circuit (106) associated with each measuring chamber (101) and connected to the fluid outlet (105) thereof, the fluid circuit (106) being equipped with a member circulation of the fluid.

7. Measuring device (1) according to claim 6, characterized in that each fluid circuit comprises one or more of the following elements:

- at least one reservoir (110) and at least one liquid injection pipe (109) connected to each reservoir (110),

- a mixing chamber (113) having an input and an output connected to the circuit fluid (106),

- at least one temperature regulator (22, 24).

8. Measuring device (1) according to claim 6 or 7, characterized in that the fluid circuit forms a closed loop inside which the medium circulates.

9. A measuring device (1) according to any one of claims 6 to 8, characterized in that it comprises means for continuously injecting liquid, and in particular at a constant flow rate, inside the fluid circuit. .

10. A method of measuring the flocculation threshold of a colloidal medium by addition of aliphatic solvent comprising the following steps:

(i) the medium is introduced inside a measuring chamber defined by fixed walls of a measuring cell operating by direct optical transmission, the measuring cell forming part of a device for measuring the flocculation threshold according to any one of claims 1 to 9,

(ii) optionally, a step of diluting said medium with a predetermined quantity of aliphatic solvent prior to step (i),

(ii) the volume of the measuring chamber crossed by the light beam, and optionally a light intensity emitted by the transmitter, is automatically adjusted using the management system so as to obtain a signal detectable by the receiver,

(iii) the flocculation threshold is determined using the flocculation measuring device after addition of the quantity of aliphatic solvent necessary for the flocculation, optionally, the aliphatic solvent is added continuously, and in particular at a constant rate, and we carry out the measurements using the measuring device while the aliphatic solvent is being added.

11. The method of claim 10 wherein the emitter emits a light beam in the NIR range and the occurrence of flocculation is determined by determining the absorption peak.

12. Method according to one of claims 10 to 11, wherein the occurrence of flocculation is determined at an adjustable predetermined temperature.

13. Method according to one of claims 10 to 12, wherein the medium comprises asphaltenes.

14. Method according to any one of claims 10 to 13, wherein the light consists of wavelengths belonging to a spectral range chosen from the near infrared spectral range and the infrared spectral range. .

15. A method of determining the stability of a mixture comprising asphaltenes by successive implementation at least twice of the method according to one of claims 10 to 14 on a medium containing the mixture and a given amount of aromatic solvent, to different dilution rates, optionally, the aromatic solvent / aliphatic solvent couple used is the toluene / n-heptane couple.